SHORT® Dental Implants: Does Size Really Matter? [HD]

Hi, my name is Bill Schaeffer and I’m here today to talk to you about one of my favorite subjects, short implants, and to try and go through with you if size really does matter or not. And I want to start with a declaration of interest, and that is that I have absolutely no financial interest in any implant systems other than that I place implants in private practice. So let’s start this lecture. Does size really matter? Well, I’m going to start by telling you what people have been telling me for years, and that’s that short implants simply don’t work. And when you look at them, they just don’t look like they will or that they should work. Little short implants with big crowns in the posterior maxilla where we know the bone is poor. Or silly little implants like this. We know from everything that some of the implant gurus like Dennis Tarnow has taught us that an implant this close to the other teeth and a stupid short one with a long crown like this, it will never work and the papillae around this restoration will never be good. Or short, round implants like this with big restorations. It’s obvious just by looking at these that they won’t work. And I can prove that they won’t work because there is a tonne of research to show that they won’t work. Here’s a great review of the literature by Lars Sennerby from 1998, and it says high failure rates are associated with the use of short implants. Another review of the literature from the same year says the same thing high failure rates associated with the use of short implants. And here’s a great paper. Here’s a paper from 2000 and it looked at the three year survival of implants of different diameters and of different lengths. And they looked at a large number of implants, almost three thousand of them, that they followed up for three years. And here’s what they found. Survival rates ranged from as little as sixty six percent for the shortest implant in the study, right up to ninety six percent for the longest implant. A third of the short implants that they used failed. A third. Can you imagine what that would do for your practice? It would destroy mine. And it specifically said shorter implants had statistically lower survival rates compared with longer ones. So short implants simply don’t work, right? Well, of course they work. Otherwise, I wouldn’t be doing this lecture. Not only do they work, they work really, really well. Let me show you the three implants that we looked at the beginning of the lecture. Five years post restoration. So that’s five year post restoration X-ray. And clinically, do they look like these are failing? No. This one that we know can’t possibly have papillae Doesn’t look too bad after seven years. And this stumpy, short, round implant with an unsplinted molar crown on top. Again, seven years post restoration. Implants are getting shorter, it’s a fact. No longer do we try to drill all the way through the entire height of the mandible to get bicortical fixation like we used to ten or fifteen years ago. Again, if we saw someone doing that routinely in this part of the mouth, we’d think they were crazy. So if implants are getting shorter, why are they getting shorter? Well, there are two main reasons for that. The first is we understand a little bit more about implants and we certainly have a lot more experience than we used to. And let me show you what I mean by that. This is a diagram of a standard screw type implant with a crown on top. And to make it really easy for you to understand what’s going on, I’m going to make this a diagrammatic implant with a lever on top. If we apply a force to that lever, to that crown, a force in the direction of that white arrow, that implant is going to want to rotate along an axis somewhere along its length. And it’s going to be prevented from doing so because it’s long and thin. It’s going to be prevented from doing so by compression of the bone on the top left and bottom right, as shown in this diagram. And the highest amount of compression will be in the centre of those contour lines, like I’ve marked in this picture. But what I want you to notice is not how much of that implant surface is being used for the distribution of compressive forces, but how much isn’t being used. In other words, the wasted area on that implant, the dead space, for want of a better phrase. If we make that implant twice as long, twice as good in many people’s eyes, and we again apply a force, it will again want to rotate and it will again be prevented from doing so by compression, as shown here. But if we compare these two diagrams, it’s not the amount of extra surface that is being used to distribute the compressive forces to the bone that’s obvious. It’s the amount that isn’t, the wasted areas or dead space on that implant. And we can imagine this if we make this implant stupidly long, a metre long, a mile long, or infinitely long. It should be obvious that if you apply a force to the crown, it’s not going to be distributed all the way down that stupidly long implant. It’s really going to mainly be distributed at the crest. But is that the main reason why implants are getting shorter? No. The main reason is because we’ve got improved implant surfaces, and by that I mean roughened surfaces. And I’m not going to start talking to you about the biology of one roughened surface against another, and how one will increase the transcription of messenger RNA and osteoblasts, because I don’t really understand that stuff. I’m a simple guy and I like to think in simple terms. And for me, a roughened surfaced implant merely means there’s more surface area of the implant to which bone can fuse. And I don’t care whose roughened surface you think is best, Because to me, it just means a roughened surface for bone to fuse to. And that’s important, because most implant systems have only been using rough surfaced implants for about fifteen years or so. So any literature reviews before about 2003 are mainly going to be reviewing literature based on machine surfaced implants, and we’ll see that later on in this lecture. Okay, how short is short? This is an ultra short implant. Well, if you look at the dictionary definition of short, it’ll give you fifty nine different definitions. But the one in relation distance merely states that short is small in length. And that’s really unhelpful, because short can then be whatever you decide is small in length for your implant practice. If you’re someone who routinely places 20mm implants, then a 14mm long implant is going to be crazy short to you. But if you write a paper that describes an implant as being short, you have to define what that length is. And to show you just how far we’ve come, there are papers describing short implants as 14mm. And throughout time, they’ve got smaller and smaller, and now short implants are generally described as being 6.0mm or less in length. Let’s have a look at the Bicon implant, because this is a system that is particularly known for its short implants. And the Bicon system is a weird, kooky, bizarre, odd, freaky, just plain strange implant system to most people. These aren’t threads. You don’t screw the implant into the bone. These are fins. So to get the implant in, you have to drill a hole that’s the same diameter as the outer edge of those fins, and then you push the implant in with your thumb. Every implant’s a spinner. Every implant’s also a pusher in or outer. Zero newton centimeters primary stability. And it’s got this weird connection between the implant and the abutment, this locking taper. There isn’t a screw that joins these two together. Instead, you’ve got a post that comes down into the implant and locks together. And they’ve got a load of short implants. They’ve got some that are 6.0mm long, one that’s a bit less than 6.0mm, and then a load that are 5.0mm long. And just take a look at this picture for a moment. Take a look at this implant here. It’s almost spherical, like a ball bearing, which is something that looks stupid for an implant shape to be. And when you drill the hole, this is the drill that you would use for that implant. And you can see that the bottom of this drill is flat. That’s the top of the implant. That’s the bottom of both the implant and the bottom of the drill. In other words, the depth that you drill to is the length of the implant. And this is important because in many systems like this Nobel Biocare implant, this is a Nobel Shorty, their short one. If you take a look at it, that’s the depth at which you place the implant into the bone. That’s the bottom of the implant, but that’s the bottom of the drill. In other words, the depth you drill is slightly longer than the length of the implant. Now, for most people, they’re only using a short implant where you don’t have much height of bone below the sinus or above the nerve. And if you don’t have much height of bone above the nerve, you damn well want to know exactly how deep you’re going to be drilling, and you don’t want to be drilling more than you need to. And with the Bicon system, you don’t have to, because the depth that you drill is the length of the implant. Here are two weird looking short Bicon implants with single unsplinted crowns on top. And they’re eleven years after they were loaded. There’s the nerve. Don’t want to get much closer than that. These short Bicon implants, they’re almost spherical. How the hell can they work? Because it doesn’t make sense to us. Here’s that same implant that I showed you earlier. And again, I’m going to make it diagrammatic so it’s easy for you to understand. If we apply a force to that crown, the implant’s going to want to rotate and it’s prevented from rotating because it’s long and thin. If you have a round implant and you apply a force, hell, it’s just going to roll over. And a short round implant, that’s definitely going to roll over, right? Well, a Bicon implant isn’t just round like a ball bearing, it’s finned like you see in this diagram. And if we apply a force, it will want to rotate. And let’s zoom in here. But it will be prevented from rotating by compressing the bone on the top left, as you see by that little green arrow, and bottom right, as you see here. But because the overall shape is kind of round, it’s not just the top and bottom of the implant that can be used to distribute compressive forces to the bone. The whole of each side can. And it’s not just each side, because these fins are three sixty degrees around the implant. So it means that almost the entire surface area of the implant can be used to transmit compressive forces to the bone. And this is important because, by definition, a short implant must have less surface area than a longer implant of the same diameter. So the more of that short implant surface area that you can use to transmit those forces to the bone, the better. And I want to be very clear that exactly the same thing happens with a screw type implant, though to an extent that depends on the depth of the threads and the shortness of the implant. Let me show you what I mean. With this implant, the deeper the threads, the more that they resemble fins, like you see on a Bicon, the more they’re going to be able to transmit these forces to the bone. The shorter the implant, the closer it gets to being round, the more of the surface area that comes into play, and the fewer the dead space, the dead areas, wasted space on the implant that isn’t being used to transmit compressive forces. And you know what? Other implant manufacturers are taking note, and they’re creating systems with deeper and deeper fins and shorter and shorter implants. Okay, where are we likely to use short implants? Well, obviously, they’re most useful where you don’t have much height of bone. And by that, I mean the posterior mandible and the posterior maxilla. I do not mean the aesthetic zone where you’ve lost height of bone. Because if you’ve lost height of bone in the aesthetic zone, and instead of grafting, you place that implant really high up where the bone is, then you’re going to end up with the platform of that implant way high up. And the only way that you can restore this is with either a really long crown or with a crown with some pink stuff on it. And that isn’t going to look good, so you better hope that your patient’s got a low smile line and a bushy moustache, because it really isn’t going to be pretty. So I’m not talking about the aesthetic zone. Short implants are most useful in the posterior mandible and posterior maxilla. And if you’re not going to use short implants in these situations, what are your other alternative options? Well, let’s have a look at the mandible first. I’m not talking about someone like Sally who’s got so much bone at the back of her mouth that you could put 14mm implants in without getting anywhere near to the nerve. I’m talking about someone like Patricia who has this much bone. She’s got tonnes in front of the nerve, but she’s only got 7.5mm above the nerve. So if you’re going to treat Patricia, what are your options? Well, the first option is you can use cantilevers, and I have no problems using cantilevers. You can put two implants in front of the nerve and put abutments and cantilever back over the nerve. It’s a great solution. I have zero problems with this, except for the fact that it’s not always possible. What if Patricia had a natural canine or a natural canine and a natural premolar still there? Well, then the only way you’d be able to do a cantilever on implants is by taking out these teeth. So it’s certainly a reasonable solution, but it’s not always possible to do that. So if you’re not going to cantilever, what are your other options? Well, you can do onlay grafting. And with onlay grafting, you chop a bit of bone out of the body from somewhere else and you screw it on top of the mandible, and that increases the height of bone that’s available for you to place your implant from this to this. But it’s not without its problems. First of all, you’ve got to dig that bit of bone out from somewhere, and that can leave you with numbness of your teeth or numbness of your lower lip. You’ve got to then bolt that bit of bone on top of the jaw and get the soft tissues to close over the top without any tension. Because if you do get tension over this block graft, you’re going to get the wound breaking down and you’re going to get saliva and food slopping down over your block graft, and that’s never going to end well. It’s going to increase the treatment time. You’ve got to wait for that block graft to bed and knit and fuse to the underlying bone, and that takes some months. And during that time, you can’t have the patient wearing a denture back there, otherwise you’ll lose all of your graft. And even if you don’t wear a denture back there, you’re going to lose about half of the height of bone that you’re trying to create with an onlay block graft. So if you don’t do onlay grafting, what else could you do at the back of the mandible? Whether you could do osseodistraction, also known as osteodistraction. Both terms are the same thing. With this, you raise a flap of gum from the buccal, but not extending past the top of the crest, not extending that flap lingually. And then you drill three lines right the way through the entire thickness of the mandible until you perforate through on the lingual side. And that will provide you with this freely floating block of bone that’s held in place and nourished with the blood supply from that lingual soft tissue that’s still attached. You can then attach a distractor of your choice, and over a period of some days increase the position of that block from there to there, allowing you to put your longer implant in. But again, it’s not without some problems. The first is that you have to drill the three holes or the three lines through the bone. And in particular, you’ve got to drill this line. Now, you’re only doing this because there isn’t much height of bone above the nerve. And you’ve got to cut right the way through the entire thickness of the mandible, just above this nerve, when there isn’t much bone there. Now, sure, you will have taken a CT scan so you’ll know where the nerve should be, but you’re making this cut without x-ray vision, and you’re having to cut close to the nerve right the way through the entire thickness of the jaw. It’s an intimidating thing to do. Secondly, you need a certain amount of height above the nerve in order to be able to fit your distractor. Here you see a distractor that’s closed and then fully activated. And you see on that diagram on the left that you do need a certain amount of height above the nerve to fit things. How much height do you need? You need about eight mils. Well, if you’ve got eight mils, you can stick a 6.0mm implant in. So osteodistraction absolutely works, but if you’re not going to do it, what else might you choose? Well, you might choose to move the nerve. And what I mean by that is you drill through the bone and you reposition the nerve so it comes out not here, but here. And that will allow you as much bone as you want to put your implant into. You can go all the way through to the bottom border if you need to. And I’ve never done this technique, but I really want to find a case where I can try it out because it’s just the kind of delicate, careful surgery that I really like doing. And I’d love to do it. But you know what? When I think about doing it, I feel a bit like this kid. I’m excited about the prospect, but I’m slightly nervous and scared. And why am I scared? I’m scared because you can make the patient numb. This is quite an old paper, but it’s by far the largest series looking at residual numbness after moving the nerves, and it’s one hundred consecutive cases. And I hate big tables like this, so I’m going to break it down for you. In this study, they looked at three different time periods after moving the nerve as to whether the patient had no numbness, some numbness, or were completely numb. And let’s take a look at these two figures. What this shows was that a week after the surgery, eighty percent of the patients that had that nerve moved were numb. Half of them were completely numb for more than a week. I know how much my patients complain when they’re numb for two hours after a normal local anesthetic. Can you imagine? Eighty percent of your patients being numb for more than a week, and in fact almost a quarter of them were numb for more than six months. And finally at eighteen months, after which time no real change is going to occur, one in twenty of his patients has some degree of numbness. So if you’re not going to move the nerve, what else can you do? Well, can do what I did. This lecture is on short implants. So that’s what we did for Patricia. I checked with guide pins, and you can see how close I am to the nerve there. And these were the implants that I placed. And here it is, more than two years after they were restored, showing very, very stable bone. Okay, that was the mandible. Let’s have a look at the posterior maxilla, which is a little bit quicker to go through. This is Justin. I really like Justin. He’s a lovely guy. He doesn’t brush his teeth enough, but he keeps coming back to me for more implants. We’ve placed three here. Since this x-ray was taken, I’ve placed some more here, but I’m looking at that right maxillary area. We want to place two implants beneath the sinus up here. And if we take a look, that’s where the bone starts, that’s where the sinus starts. So we’ve got about 6.0mm at the front, 6.0mm at the back and a little bit less in the middle. What are your options? Well, the first option is a lateral sinus graft, A Caldwell-Luc approach, lateral window graft. Loads of terms for the same thing. And we all know what this is. You raise a big flap. You drill a hole through the bone covering the sinus, but not through the membrane that lies immediately beneath it. And that produces a little window of bone that’s now bouncing up and down on the membrane. And you can either leave that attached or remove it. But it gives you access to that membrane, allows you to free it up from within the inside of the sinus. Work your way around freeing that membrane up. And eventually you’ll see that little bit of bone that was vertical is now lying up horizontally and creates space beneath it, into which you can pack the graft of your choice that week. There it is. And with this technique, you can increase the height of bone at the back of the maxilla to this, or you can go crazy if you like and fill it as much as you want. You only really need that much extra height because that’ll give you implants this long. But that technique is not without its problems. You’re going to elongate the treatment time because it’s not the patient’s own bone. It’s going to take time to become a living part of them. It’s not very comfortable. And I find that whether patients get bruising and swelling despite giving patients steroids beforehand, it’s very unpredictable. This lady worked for the BBC and she really wasn’t happy with me when she got some bruising. But this is a lady for whom I did bilateral sinus grafts on the same day. So one side has no bruising and swelling and the other one looks like she’s been in a fight. But is that the complication that I’m most concerned about with lateral sinus grafts? No. The one that I’m most concerned about is infection. These are the figures from Hilt Tatum who developed this technique. He says that despite giving antibiotics before the procedure and after the procedure, despite mixing the graft with a different type of antibiotic, you’re going to get infections affecting about three percent of all lateral sinus grafts. Of that three percent, you can settle down two thirds with a further course of antibiotics, but that still leaves one percent of all lateral sinus grafts that develop an infection that you cannot settle down easily with antibiotics and necessitate you removing the graft. And imagine what that means for the patient. They’ve gone through the first surgery, they’ve had infection, you have to remove that. And remember, it’s not easy to numb patients up when there’s infection. And finally, after removing the graft, you’ll get that patient healthy again. And what do they have to look forward to if they still want teeth there? Well, if they want implants in that position, they ‘ve got to look forward to yet another lateral sinus graft. So if we’re not going to do that, what is our other option? Well, can do an internal sinus lift, also known as an osteotome technique or Summers’ technique. And I’ve seen papers with Sommer spelt all three of these ways. It’s the middle one that’s correct. And in this, you drill a hole up to the floor of the sinus, but not through the bony floor. You then gently tap up with an osteotome, and that allows you to put some graft in, enabling you to put a longer implant in than you would have otherwise been able to do in that amount of bone. And it’s a great technique, but again, it’s not without its problems. Firstly, it’s a closed procedure, so it’s difficult to spot a hole, let alone to repair one if you find it. It’s a very straightforward procedure when the floor of the sinus is flat, But if the floor of the sinus is sloping, it’s very challenging to know what height you should be drilling to. And most people would state that you can only get a very limited gain in height, 2.0-3.0mm at most. My feeling is that the amount of height that you can gain is limited by your skill and experience and by the anatomy of the sinus floor that you’re lifting. And you can get some great gains in height, like you see with Alice here. Alice actually has zero bone. She has a hole in the crest where the periosteum of the alveolus is fused with the lining of the sinus. And for her we’ve raised a very small flap. This is not the size of flap that you would use for a lateral graft. This is the kind of flap that you raise for placing an implant. And we lift the membrane, pack some graft, and that’s what it looks like on the day of surgery, and that’s what it looks like four months later. And you can see the before and after here. You can get quite a lot of gain and height if you know what you’re doing and the anatomy of that area allows you to do it. But is that what I did for Justin? No, I placed two short implants. These are slightly wider than they are long. 6.0mm wide, 5.7mm long. No sinus grafting of any kind was needed because they’re only 5.7mm long and 6.0mm of bone. And here they are eighteen months post restoration and about two and a half years after restoration. Single unsplinted molar crowns in the posterior maxilla where we know the bone is poor, on short, round implants. You’re going to see a ton more cases in a moment. So look, short implants obviously have some advantages over all the other options that we’ve been through there. First of all, there’s no increased morbidity. I don’t have to dig a bit of bone out of somewhere for a block graft. There’s no chance of numbness. There’s no risk of dehiscence over a graft or of infection of a graft. There’s no increased treatment time. I don’t have to wait for a blocked graft to fuse a distracted segment to become solid or for a lateral sinus graft to become a living part of the patient. There’s no problems with temporisation. If you want to bury the implant and stick a denture on top, that’s easy. And it’s routine implant dentistry. What I mean by that is this: if you can drill a standard length hole for a standard length implant, you can drill a shorter hole for a short implant. What you’re not having to do is send the patient off to the scary oral surgeon for a scary bone graft. And please don’t make too little of this. Grafting is expensive. It really is. And especially when the grafting is done only for one or two implant space. It can push the cost of treatment outside what is affordable for the patient. So obviously short implants have a number of advantages, but are they really as attractive as they first appear? Or is there something about them that we’re missing? Are they really safe? Or is this a treatment that’s going to turn around and bite us in the butt? But in other words, do they really work? So let’s look at the evidence. This is the seminal paper written by a hero of mine, Franck Renouard, and his business partner David Nisand. And this is the paper published in Clinical Oral Implants Research in 2006. And it was also a literature review, a bit like the ones that we saw at the beginning of this lecture, but over a sixteen year period. And it defined a short implant as a device that’s into bone to 8.0mm or less. And it came up with these conclusions. A relatively high number of published studies, twelve of them, indicated an increased failure rate with the use of short implants. Implants. Doesn’t look good. But then it goes on to say, but more recent publications, almost double the number, have indicated survivor rates of short implants exactly the same as those obtained with longer implants. And it goes on to say, it is noteworthy that articles dedicated to short implants published in the last three years of this study have reported survival rates ranging from ninety four point six up to ninety nine point four. The worst study out of all twenty two that they could find still had a survival rate of ninety four point six percent. That was the worst results they could find. And it talks about why there were these differences between the older studies and the newer studies looking at short implants. And it says that they may be explained by differences in the implant surfaces. Because of the twelve studies that showed a worse outcome with short implants, eleven of them used machine surfaced implants and the remaining one used a mixture of machined and coated implants. Here’s another review of the literature and meta analysis. More recent, 2009. And it says, and I love this conclusion, just look at the wording. Within the limitations of this review, the placement of short, rough surfaced implants is not a less efficacious treatment modality compared with longer implants. You see, you’re having to drag out of them. They can’t say short implants work just as well as long ones. How hard is it for them to say that? Instead, all that they can bring themselves to report is they’re not a less efficacious treatment modality. And here’s a great study done by a great guy, Marco Esposito. Marco is the researcher who heads up the Cochrane database. So he really knows how to conduct a study, and this is a great study. There were fifteen bilateral atrophic mandibles and fifteen bilateral atrophic maxillae. And he randomized these jaws to a split mouth study design. It’s already starting to sound good. And these patients either got, on one side, they got one, two or three short implants, 5.0mm long implants. And on the other side, they got at least a 10mm long implant in augmented bone. And how did they augment the bone? Well, in mandibles, it was a block graft. And in the maxillae, it was a lateral sinus graft. And they looked at all the normal things that you would expect them to look at. What did they find? They found that in five, so a third, of the mandibles that they grafted, they couldn’t get the 10mm long implants that they had hoped to, so they had to put something a bit less than 10mm in. And in terms of the failures, two of the longer implants and one of the shorter implants failed. That wasn’t statistically significant, but what was, was when they looked at the effect of implants on the crestal bone. So shorter implants lost significantly less bone than the longer implants in grafted bone. And he goes on to say this pilot study suggests that 5.0mm short implants can achieve similar, if not better, results than longer ones placed in augmented bone. And that short implants might be a better choice than grafting to get longer implants in, since the treatment is quicker, cheaper and associated with less morbidity. Now Marco has repeated this study three more times to this date, and each time he’s done it, he’s found complications associated with the grafted group. Graft loss, dehiscences, infections, problems. No problems with the short implant group. Now, I can show you a ton more papers because all the recent papers show short implants working as well as longer ones. But you don’t want that. You want to see more examples. So let’s have a look at some. Look at the middle implant placed in February 1997. Here it is two years post restoration, five and a half years, eight years. Let’s zoom in on that eight year picture. That’s the bottom of the implant, that’s the top of the implant, and that’s the top of the crown. So that’s the crown root ratio. That’s wrong. Most teeth, even ones with a bit of periodontal bone loss, have longer roots and crowns. Yet the implant here has a longer crown than root or length of implant. Both implants placed eight point nine seven, so that’s eight months. Seven point five years, nine years. Look at the crown root ratio. Much longer crown than root. Implant placed May ninety seven, so four and a half years, seven years, eight years, eleven years, thirteen and a half years. Single, unsplinted molar crown on a round, short implant in the maxilla where we know the bone is weak. Look at the crown root ratio. Look at it on the adjacent teeth, which have longer roots than the crown. Look at it on the implant, which has a much longer crown than the root. And some of you might be thinking, well, the only reason that implant stayed in there for so long is because it’s not an occlusion. Yeah, it’s an occlusion not just with the tooth, but also with an implant. Another one, seven years, eight years, longer crown than root. Look at the crown to root ratio on this. Compare what was a natural tooth next door. Short round implant in a tiny bit of bone in the posterior maxilla. Three years on, four years on, six years on. Look at the crown root ratio. But this next one’s my favorite. What a screw up! Look at that implant! Was the surgeon drunk? It’s a crazy situation. Everything in our implant souls tells us that this cannot possibly work. Single, unsplinted molar crown with a mesial cantilever, off axis loading, on a short round implant in a distal extension situation where we know the forces of occlusion are highest. This cannot work. Four and a half years, seven years, eight years. Both of these ten years. I thought these two x rays were the same when I first put them up, they’re not if you look closely. It’s eleven years and here again thirteen and a half years. I don’t even know where you would measure the crown root ratio to. Would you measure it like this or like this? I don’t know and I don’t care. Because thirteen and a half years on, and just look at the bone around this. These crown root ratios really are crazy because when we look at what we are taught about restoring natural teeth, we are not supposed to have longer crowns than roots on our teeth. If possible, we want a one to one and a half ratio. But if we really have to, the minimum ratio for a prospective abutment is one to one. Here is a natural tooth. At the moment, it has a crown root ratio of one to two. If we lose a bit of bone from around this root, now it has a crown root ratio of one to one. If we lose yet more, that is a crown root ratio of one and a half to one. Just one and a half to one. I don’t think many people would want to put, would want to use a tooth like this as a bridge abutment. By definition, a short implant is going to have an unfavorable crown root or crown implant ratio. But do the normal crown root ratio rules of natural teeth actually apply to implants? Well, here’s quite a nice paper, a ten year prospective study. And it looked at almost two hundred implants over ten years. And it looked specifically at the crown root ratio and how it affected the crestal bone. And they had three groups. A crown root ratio of less than one, one to two, or two or more. And a quarter of the implants studied had a crown root ratio of two or more. What did they find? They found that implant restorations with high crown root ratios showed significantly less bone loss than implants with normal or low crown root ratios. Less bone loss. The crazier the crown root ratio, the better the crestal bone was. And it says implant restorations with high clinical crown root ratios do not demonstrate lower survival or success rates when compared with implant restorations with lower crown root ratios. And as a result, the use of implant restorations with crown root ratios as high as two or three may be successful in the posterior region of the mouth. Crown root ratios of three to one. Remember this tooth. This has a crown root ratio of one point five to one. This paper is saying you can have crown root ratios of three to one with implants and still be perfectly successful. Here’s another paper from 2009. Technical complications related to crown root ratio were not found in any of the studies. And in addition, the peri implant bone loss was not influenced by the crown root ratio, except in one study where the crazier the crown root ratio was, the better the bone. So if the crown root ratio rules of natural teeth don’t apply to implants, why don’t they apply? There are three reasons. The first is, crowns have conical roots and implants are cylindrical. I know you can have tapered implants. Come on to that in a moment. Let’s take a look at this tooth. It has a tapered or conical root, and it’s really conical when you get down to the apex of that root. If you lose half of the bone, the half of the height of bone from the root, you have lost much more than half of the bony attachment. This implant is half the length of this implant. It’s got half the bony attachment, not much less than half the bony attachment. Don’t worry too much about this one, it’s the least important of all the reasons. Health versus disease. These two things are in bone to the same height. But this one is supposed to be in bone to that height. This is supposed to be in bone to that height. And here’s where we come on to tapered implants. You don’t place tapered implants just at the very bottom of the taper. You place tapered implants to the full depths of the implant. Just like this one. But are those two the main reasons why crown root ratio rules of natural teeth don’t apply to implants? No. The main one is that implants don’t have a periodontal ligament. They are more like an ankylosis. Let me show you what I mean. Let’s start by imagining we’re going to take out a lower premolar in a healthy tooth. And let’s say we’re going to do it with a pair of extraction forceps. I know we don’t normally take teeth out with a pair of extraction forceps these days. We use luxators or periotomes. But let’s imagine we’re going to do it the old fashioned way. Let’s imagine we’re to take a natural, healthy lower premolar tooth out with a pair of forceps. You will stand behind the patient, you’ll grip the patient’s head with one hand, you’ll apply the forceps to the tooth with the other, and then you’ll give it a bit of force. And you’ll start to gently wiggle that tooth. And because that natural tooth has a periodontal ligament, there will be a bit of wiggle. And you’ll be able to gently increase the amplitude of those movements that you make forwards and backwards, maybe figure of eight, gradually increasing the amount that you can move that tooth until you roll the tooth out sideways. We’ve all done it. Let’s imagine now that instead of taking out a natural healthy tooth, you’re taking out an ankylosed tooth, an ankylosed lower premolar. You stand behind the patient, you grip the head with one hand, you apply the forceps to the tooth with the other, and you start to apply some force and crack. You cannot take out an ankylosed tooth with a pair of forceps. Long before the bone root interface breaks down, you’ll have snapped the crown off. How do you take out an ankylosed tooth? You cut it out. Let’s imagine now that instead of an ankylosed tooth, you’ve got an osseointegrated, effectively an ankylosed implant. And let’s, I know it will seem silly, but let’s just imagine you’ve got a premolar implant perfectly healthy with a really strongly attached crown on top of it and that you’re going to try and take it out with a pair of forceps. Just bear with me. So let’s imagine you grip the head with one hand, you apply the forceps onto the implant crown with the other, and you really start to apply some force. I don’t care how strong you are, you cannot take integrated implant with a pair of forceps. Long before the bone implant interface breaks down, you’re going to have broken the crown off, broken the implant, broken the forceps, dislocated the mandible or even fractured the mandible. How do you take out an integrated implant? You cut it out. Trephine it out. Look, a natural tooth with a periodontal ligament has a bit of wiggle and it’s a bit like a fence post buried in Earth. If you don’t have much buried in Earth and you have a lot sticking out, it’s going to wiggle and before you know it, it’s going to fall out. So how do you keep that fence post solid? You bury a lot of it in the earth and you don’t have too much sticking out, just like a natural tooth. An implant, on the other hand, is like a fence post buried in concrete. You really do not have to have very much buried in concrete to be able to have a long post sticking out and still have that very, very strong. Take a look at this Ferrari that’s driven into this traffic light. How much of that traffic light is buried in the concrete? Two foot, maybe three foot. You can drive a Ferrari straight at it, and the Ferrari comes off much worse. If you think that’s a one off, Ferrari drivers like to drive into things. So do other drivers. Now, you may bend the post. You may buckle the post. You may scratch, dent, ding, bash up the post. But what you won’t do is rip it out of the concrete. And an implant in bone is just like this. You don’t have to have very much buried in the bone to be able to support and withstand large occlusal forces on it. Okay. We’ve seen that you can have short, fat implants, because I’ve shown you a ton of them. We know from our own experience that you can have long, thin implants. But can you have a short, thin implant like this? Because let’s face it, that would be the answer to our problems. You wouldn’t need much height of bone, and you wouldn’t need much width of bone. You wouldn’t need much bone at all. Maybe the end to grafting. Well, the answer to that question is yes, it does work, and no, it doesn’t work. And obviously on this picture you can see the no is bigger, so we’re going to start with why a short thin implant doesn’t work too well all the while. Well, firstly, you do need a certain minimum amount of bone implant contact to be able to withstand occlusal forces. You can’t have an implant the size of a pinhead and expect it to be able to withstand the normal forces of chewing. But is that the main reason why short thin implants don’t work so well? No, the main reason is this one. They break. And where do they break? Well, they either break at the top of the implant or at the bottom of the crown, the screw, somewhere in that region. But hang on a moment. Why should that short, thin implant break there when that part of the long thin implant is identical to it? And I like this part of the lecture because it makes people think. The reason is that you don’t place a short thin implant in that position. You normally place a short implant where there isn’t much height of bone, which means that you’ll have a long crown on top. And this short, thin implant has thin, weak walls and won’t be able to withstand the forces of leverage applied by a long crown. And it will break. And I can hear you saying, hang on, that’s crown root ratio. You spent the last ten minutes telling us that crown root ratio doesn’t affect implants. Now you’re saying it does. You’re contradicting yourself. You’re an idiot. Shut up and go home, right? I am not talking about crown height to implant length. I’m talking about crown height to implant strength, which is directly related to implant width. Let me show you what I mean. This short, thin implant has exactly the same crown root ratio as this short, fat implant. But this short, fat implant has thick walls of titanium, big, thick, strong screws. It’s never going to break. It’s easily able to withstand the forces of leverage applied by that long crown. By contrast, if we take this long thin implant and we bring it down to the same height as the short thin implant, they now have very different crown root ratios. But if this implant is too thin and weak to withstand the leverage of a long crown, then so will this one be, and it will break. And that brings us on to something very interesting. If we go back again to this standard generic screw type implant, and we imagine overloading it to the point of failure, if we did, it would break somewhere here. Making that implant longer doesn’t make it stronger. Only making it wider will make it stronger. And that’s interesting because we’ve always been taught longer is better, longer is better because longer is stronger. No, it isn’t. Only wider is stronger. Well, I did say that a short thin implant could work well. And what situation is that? Well, it’s this situation here. If this long, thin implant is strong enough to withstand the forces of leverage applied by a short crown, then so is this. But most people wouldn’t usually place a short implant in a situation where you’ve got stacks of bone. They’d usually place a longer one. Come on to that later. But hang on a moment, I hear you all shout. What about all those studies that show damaging crestal bone stresses with short implants? And by that, I mean photoelastic modelling of finite element analysis studies. Well, let’s get rid of the first one very quickly. Photoelastic modelling, as you may remember, is you stick an implant into a homogenous block, clear perspex. You apply a load to it whilst looking through polarized filters, and you see lines of force around the implant. Bone isn’t a homogenous block of perspex, so we can just move on from photo elastic modeling. Move on to finite element analysis. This is computer modeling of stresses and strains, loads, forces. And when it first started, you can see from this computer model from the early 90s, the models were fairly crude. These days, the models are very sophisticated. And we see pictures like this of the bone around an implant. The implant’s being removed and immediately, intuitively, you can understand what this picture shows us. It shows us crestal bone strains in red. And we know red is bad, red is danger. Red will mean the bone will be lost. Green is good, green is safe. Green will mean the bone will be saved. And finite element analysis studies are really popular. Why? Because they’re easy for universities to do. You don’t need an ethics committee approval, you don’t have to find patients, don’t have to follow them up with dropouts, you’ve got no complications, no follow-up. It’s cheap and it’s quick. Most universities get funding based on the number of papers they produce. This, you’re able to really quickly get out papers. You do one paper on width, hey, change the parameters in your computer, look at length, look at anything you want, you get another paper out. But there’s a problem with it, and the problem is it’s not real. It’s not real because it’s not alive. Finite element analysis is really good at looking at inanimate things, like a bike frame being subjected to load. But we never see videos like this of the stresses and strains around an implant. We only ever see still pictures. And the reason for that is if this was a video, the lie that we’re being told would immediately become obvious. Because when we chew, when we apply these forces to the bone, we don’t bite together and keep biting together forever. We bite and we release. Remember that force on bone is related to amplitude, duration, frequency and direction. And we’re changing all of those all the while when we chew. And then, in between those episodes of chewing, we’ll have long episodes where there’s no forces being applied to the bone. Periods where the bone can do what it does best. It can respond by making itself stronger. This is no different from going to the gym and doing bicep curls. You don’t stay there with the weight halfway in your bent arm for a week. You do a few curls and you go back to the gym in a week. Now, the next two days, your bicep’s going to ache. Why does it ache? It’s because you’ve damaged it. I don’t mean damaged it to the point of failure. You haven’t ripped the tendons out of the arm. But you’ve damaged it, and that’s why it aches. And what happens over the next week? The arm responds, the muscle responds by getting stronger. So does bone. If this girder was a living thing, every time you loaded it, it would get stronger. Look, we’ve been taught that high loading is bad for bone. Why on earth would anyone think that? Bone is a living thing like a muscle. We don’t say to our little old osteoporotic ladies, Mrs Smith, your bones are weak. You must lie down flat on a bed and not move, because if you do, your bones will break. Of course we don’t. We say, Mrs Smith, your bones are weak. You’ve got to go out and exercise to make them stronger. That’s what bones do when you load them. Take John. John is seventy two, and twelve years ago he had these implants placed. In fact, twelve years ago he had a load more implants placed, but another dentist somewhere else removed some implants on the top right, promised John that he’d replace them, and then went, oh, I’m sorry, John, there’s not enough bone. So he had been surviving with what you see on this x-ray for more than six months on these implants that are twelve years old. This is what his mouth looks like, and that is all he is occluding with. What you see touching is all that’s touching in his mouth. He doesn’t wear a denture, hasn’t had one made. He’s been biting for just over six months just on what you see touching there. Nothing on the other side. That’s all that he’s been occluding on. What does the bone look like around these presumably overloaded implants? Well, you know what? Not too bad. In fact, in the upper jaw, where we know the bone is weaker, also not too bad. And I can hear you say, well, perhaps he hasn’t been loading them. Perhaps he’s only been living on a liquid diet. Well, know he’s not been living on a liquid diet because two weeks after this x-ray was taken, he came in like this. And can you see? He’s fractured that implant. So he has overloaded this implant to the point where it breaks, but only now does the bone start to disappear. Previously, the bone was great. Bone responds to the forces applied to it. Look at these x rays seven years apart. Look at the bone, eight years apart here, seven years apart here. Look at the bone. Again here. Bone responds to the forces applied to it. Listen, finite element analysis, those computer modelling studies, they tell us that short implants are going to load the bone really high, and when that loading is high, you’re going to lose the bone. The clinical studies that I’ve shown show the same or better bone around implants with a high crown ratio. So short implants, long crown, high crestal bone forces. Which one is right? The computer modeling or the experimental evidence? Which one is right? Well, Richard Feynman, the Nobel Prize winning physicist, he said, it doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are, if it doesn’t agree with experiment, it’s wrong. Finite element analysis modeling is just that, it’s modeling a theory. It doesn’t agree with the experimental evidence that we see in the clinical studies, where the bone is the same or better with short implants and long crowns. Therefore, the finite element analysis is wrong when it talks about bone being lost because of high loading. And that brings me on to one other topic, micro threads or MicroThreads™. And we all know what micro threads are if we zoom in on this cutaway. It’s these finer threads that you find at the top of so many implant systems. And we are told by the implant manufacturers that they do this for us, that they put these micro threads on their implants to reduce the crestal bone strains, the crestal bone loading, because by doing that they will maintain the bone better around these implants. They’re doing that for us and our patients. How nice. That’s not why they’re doing it. It’s not why we’ve got micro threads on so many implants. This is why. Let’s look at the cutaway part of this implant on the left of the picture. That’s the outside part of the internal thread at the bottom and at the top. And that’s the inside part of the external thread, at the bottom and at the top by the micro threads. So that’s the wall thickness lower down, and that’s the wall thickness higher up where you’ve got the micro threads. That’s still quite thick, that’s quite strong. Let’s imagine now that we’ve carried those thicker threads all the way up to the top of the implant like this. Now, if you look, that’s how wide, how thick it used to be with the micro threads, and that’s how thick it is now. That you’ve removed the micro threads and got the normal threads all the way up. Now that isn’t thick enough to withstand the forces of chewing. This implant is too weak. This implant will break, split, flower. But is that what they tell us? They’ve put the micro threads on for? Do they say, we’ve put micro threads on your implants to stop our implants from fracturing? No. They spin it, and they say, we’ve put micro threads on to prevent crestal bone loss by reducing the crestal loading. It’s nonsense. The more you load bone, the better the bone is. But everyone’s selling the same thing. I’ve been saying how great short implants are, but are there any situations where you shouldn’t use short implants? Yeah. If you’re putting an implant into a socket, let’s face it, the crestal part of the socket is big and wide. It’s a big empty hole. You only can get the implant solid and stable if you go down deeper. You need a longer implant for that. If you’re immediately loading your implant, you want good primary stability, primary fixation. And for that, you’d want to use a longer implant. And also, if you’re putting an implant into an area where there isn’t much bone and you know that 6.0mm of that implant are going to need bone grafting over it because it’s sticking through the side of the bone, then you want a longer implant, so at least you’ve got some of your implant fully in bone, keep it stable. But let’s take a look at this. Look at this case where you’ve got loads of bone, 16mm of bone above the nerve. What are the advantages and disadvantages of putting a longer or shorter implant in it? Let’s just imagine two. Let’s imagine a 12mm implant or a 6.0mm implant. What are the advantages of each of those? Well, advantages of putting that longer implant in is that you can load it immediately, or if you don’t load it immediately, you’ll load it earlier. Most people wouldn’t immediately load a molar, there’s not much need to. But even if you don’t load it immediately, you might be more comfortable taking impressions earlier than if it was the 6.0mm implant. By the same way of thinking, you might be more comfortable putting the 12mm implant in as a one stage surgery, so with a healing abutment on top, whereas for the 6.0mm implant, you might be more comfortable if you bury it beneath the gum. And finally, let’s face it, you can lose a bit of bone around that longer implant and the implant will still be stable. What are the advantages instead of using that shorter implant, that 6.0mm implant? There’s no advantage about being safer above the nerve because, hey, the 12mm implant is safe above the nerve when it’s 16mm of a bone you’ve got. No, there’s only one advantage of using a shorter implant, and that’s that it’s easy to remove and replace the shorter implant, even if you’ve lost some bone. Now, that’s kind of odd because that’s almost the opposite of what I said at the end of the last slide. I said in the last slide that a longer implant is a better implant because if you lose some bone, it can still be stable. Here I’m saying that a shorter implant is a better implant because if you lose bone, you can replace it easily. What do I mean by all that? Well, what is the worst thing that can happen to a well placed implant? It’s not that it doesn’t integrate. That happens sometimes, not very often, but our patients have always been warned about it happening. The implant fails before it’s integrated. You take it out, you let it heal, you put another one in. It’s really not a big deal. The big deal comes when an implant integrates and then it starts to lose bone. Take this patient as an example. This patient had a beautiful 12mm long implant placed here, and it was restored by one of our prosthodontists, specialist prosthodontists. It’s got a beautiful screw retained crown, so no cement to cause problems. It’s a prosthodontic type of fit to all the components. Immaculate fit. And it’s a prosthodontic type of occlusion. Perfect. No high spots. This patient came back two and a half years later with this, saying that something felt a bit odd. Hadn’t been back in the meantime. There’s a nerve, there’s the bone. That’s a 12mm implant. So it’s lost 8.0mm, but it’s still got 4.0mm in there. It’s rock solid, it’s not going anywhere. Is it better because it’s 12mm? Or would that implant have been better if it was a 6.0mm implant? Is this implant a good implant because it’s so long and therefore still hasn’t been lost? Or would it have been better if it was short? Is this implant a good implant because it’s still got four or 5.0mm holding in the bone? Okay, yeah. It stripped all the bone off the adjacent teeth, but the patient’s still got her implant. Is that good? I’m not so sure. If we go back to this case, what do I do when I’m presented with a situation like this? I put the shortest possible implant that I can into that site. And I appreciate that many of you looking at this video will think that that is crazy. They’ll find it very hard to understand. They’ll say things like, Bill, hey, I can understand why you might want to put a 14mm implant in there, but hell, you can put a twelve or a ten or even an eight. Why would you want to go down to one of these crazy short implants? You’re an idiot. I can completely understand anybody feeling that way. But you have to remember two things. The first is I don’t only place short implants, I place a tonne of conventional implants, because I do a lot of immediate loading, put a lot of implants in sockets, and I place implants where there isn’t much bone and I need to do GBR over the top of them. I place a lot of conventional length implants. But here’s the big kicker. I consider a short Bicon, once it’s integrated, a 5.0mm long Bicon to be at least as good, if not better, than a 14mm long one. Now most of you watching this video, if you’re used to placing conventional length implants, you’ll look at a case like the x-ray that I showed you a second ago, and you’ll look, well, I’ve got 16mm. Well, I might want one of fourteen, but maybe I can get a twelve. Or you’ll work your way down because you think that a longer implant is a better implant. I think a short implant is at least as good as a longer implant. So I look at that X-ray and go, can I get a 5.0mm implant? I don’t have to think anything further than that. I want to make it very clear that I am not suggesting that short implants are good and longer implants are in any way bad. I’m not. I place a lot of longer implants. I’m not suggesting that anyone that places longer implants grafting is doing anything wrong. I place longer implants and I do grafting. I’m also not suggesting that any of you need change, anything that you’re currently doing. All I am suggesting is this: conventional implants work really, really well, and so do short implants. Look, I don’t have any shares in short implants. It means nothing to me if you use them or do not. But if you do start using short implants, what might it mean for your patients? Well, for your patients it means one thing less bone grafting. And what that means is less painful treatments with less morbidity, done more quickly, done by you and not the scary oral surgeon. Easy to temporize if you want, just bury the implant, put a denture on top if you need to. And don’t forget, more affordable for the patient, because the treatment’s going to end up being cheaper. That’s what it means for your patients if you use short implants. What does it mean for you? It means you’re going to be placing an awful lot more implants, Patients don’t want bone grafts, patients just want replacement teeth. And if you can provide that for them more simply, quickly, less painfully, and more cheaply, you’re going to put a lot more implants in. Look, the simple truth is that short implants work. It’s a fact. The evidence now is overwhelming. I’d like to say a big thank you to clinicians who provided me with some of the cases that I’ve shown when they weren’t my home. I’d like to thank Bicon for doing this video, allowing me to show what I believe to more people. And most of all, all of you for your kind attention. Thank you for listening.